The daily and seasonal vocalization of the red fox was traced. Year-round studies were carried out using digital voice recorders. Fox barking was recorded in the frequency range from 700 to 3600 Hz. The cackling of the fox was recorded in the frequency range from 500 to 2500 Hz. Fox calls were recorded in all seasons of the year, but the most pronounced peaks of prolonged activity in the year were recorded in spring and autumn. The vocal activity of the red fox was noted for the entire period of the study from 17:51 to 01:38. During this period, the total duration of calls in the red fox varied from 34 sec to 27 min per day, 4 min on average. 86% of all call registrations in the region occurred before midnight, the rest (14%) after midnight. Vocalization began after sunset for an average of 2 h 49 min.
Andreychev A. Vocalizations by red fox (Vulpes vulpes) in natural and climatic conditions of Mordovia (Middle Volga region)// E3S Web of Conferences 462, 01004 (2023).

We recorded vocal interaction in the natural environment of an Eurasian Eagle-Owl (Bubo bubo) with canines Gray Wolves (Canis lupus), Red Foxes (Vulpes vulpes) and domestic dogs (Canis familiaris). Vocalization was recorded using Olympus digital voice recorders. The calls of the male Eurasian Eagle-Owl were recorded by us in the frequency range of 200–420 Hz. The howl of a Gray Wolf was recorded in the frequency range from 300 to 1,100 Hz. Red Fox barking was recorded in the frequency range from 750 to 1,000 Hz. Barking of domestic dogs was recorded in the frequency range from 250 to 1,500 Hz. The vocalization of the Eurasian Eagle-Owl had an independent character inherent in the biology of the species. The Eurasian Eagle-Owl, with its cries, involuntarily provoked the entry of canines into joint vocal interaction, which can be explained by the high social activity of the latter. Co-vocalizations of the Eurasian Eagle-Owl and canines were noted in winter, spring and autumn, but mainly in spring (50%). The increased use of autonomous voice recorders, which record spontaneous vocalizations emitted by animals over long periods, will allow us to better document and study the importance of such interspecific interactions.
Andreychev A. Vocal interaction between Eagle Owl (Bubo bubo) and canines (Carnivora, Canidae) // Ornis Hungarica. 2023. V. 31. № 2. P. 61–73.

The article describes the characteristic of the camouflage device for the camera trap, which was effectively used in the study of diurnal and seasonal mammals and birds in the central part of European Russia. In the masking used, the principle of mimicry is used. The masking device makes it possible to successfully use camera traps in any season of the year with the aim of studying animals or conducting tracking in hunting facilities. Daily activity of common fox Vulpes vulpes, badger Meles meles, Eagle Owl Bubo bubo, marmots Marmota bobak.
Andreychev A., Lapshin A. The effectiveness of using a masking device for a camera trap in studies of mammals and birds // Research Journal of Pharmaceutical, Biological and Chemical Sciences. 2018. 9(3). P. 1009–1016.